The result is a more artistic interpretation than scientific reproduction. For example, many of his works involve complex color blends in which more than one ink color is printed through the screen at the same time. Petro developed the unique blending technique, which has become one of the signatures of his artistic style. He explains that the colors do not blend identically throughout a series: "The blend will gradually spread, and you might get three or four prints and then take out the screen and reblend the colors. If you reverse blends and just keep blending, it will give depth to the piece and shadowing." The result is a powerful three-dimensional effect on a flat piece of paper (Figure 3).

Three decades of experience have given Petro the necessary background to understand what kinds of effects can be created with this raw style. And he's not afraid of experimenting to find new effects. "You might hand cut part of the image and then draw the other part with opaque on acetate and combine the two, which can give you a very sharp edge with very loose brush work and splatters," he says. "You can do almost anything with screen printing to get the effects you want, which is kind of fun. And sometimes mistakes work out pretty well."

Petro prefers printing on a textured, rather than smooth, paper. "It's usually 290-gram, machine-made, cotton Coventry rag," he explains. "It has a pretty sturdy, hard finish--not smooth. I don't like the real smooth gloss finish because the ink is going to be mottled a little. I prefer it soaking into and not sitting on top of the paper. A lot of early screen prints I've seen from the '60s, '70s, and early '80s crack when they use gloss poster and the ink sits on top of the paper. I like to stain the paper."

Rather than butt register his colors, Petro prefers to overlap his inks by 1/16-1/32 in. "That way you use the white paper underneath, which makes the color brighter," he says. "If you're out looking at a tree or a fence or anything, there's always an outline. I use that outline as basically another color when you've got the overlapping of two colors."